Apple tree named `M9-RN29`

ABSTRACT

This invention relates to a new and distinct apple tree rootstock clone which is useful as a size controlling rootstock. The new clone originated as a mutation of Malling 9 (M9), an unpatented dwarfing apple rootstock. Standard growing apple cultivars propagated on this new rootstock are approximately 65% of the size of like apple trees growing on seedling rootstocks. Compared to its M9 parent, this new clone produces many more and larger lateral branches, has more sharply serrated leaves which are more pale yellow-green in color. The clone is also more vigorous and produces a large number of rooted plants in a given area of stoolbed.

This is a continuation of application Ser. No. 07/642,992 filed on Jan.18, 1991 (now Abandoned).

BACKGROUND AND SUMMARY OF THE INVENTION

The inventor of the subject plant, Rene Nicolai, was the owner of ReneNicolai Nursery, which propagated and sold Malling Nine (M9) apple treerootstock. Rootstock are propagated by placing plants in a stoolbedwhich encourages root growth and then dividing the resulting roots intoindividual plants. Over the years Mr. Nicolai searched the M9 stoolbedsfor M9 mutants which were superior to the parent variety in thosecharacteristics which are desirable for apple tree rootstock.

The subject clone was selected in 1967 from a large stoolbed of M9plants that was planted in 1960 at the Rene Nicolai Nursery atLinderstroot, 22-B-3820 Alken, Belgium. The original source of theplants in the bed was the East Malling Research Station in England.Following its selection, the clone was assigned a number (RN29) and waspropagated for further testing and evaluation.

Since all original M9 rootstocks have been found to be virus infected,RN29 stocks were subsequently heat-treated by application of dry heat inorder to obtain virus-free specimens. After heat treatment andsubsequent virus testing, the new rootstock clone was again exposed tomultiplication techniques (stooling) followed by continued testing andevaluation.

Virus-free RN29 progeny plants were expanded into small stoolbedplantings at several locations which were planted separately in order toexamine the new variety's individual characteristics in smallsemicommercial stoolbed sites. Since 1974 nearly 40,000 plants of thesubject variety have been planted at the following six sites and, in theprocess, many generations of the tree have been produced:

1. A site at Deveaux, Belgium was planted in the spring of 1974 with1,875 plants of the subject clone.

2. A site at Bordeaux, France was planted in 1977 with 200 plants of thesubject clone.

3. A site at Wissenhoeve, Belgium was planted in the spring of 1980 with7,644 plants of the subject clone.

4. A site near St. Truiden, Belgium was planted in the spring of 1982with 100 plants of the subject clone.

5. A site at Henkaenrts, Belgium was planted in the spring of 1986 with3,250 plants of the subject clone.

6. A site at Ephrata, Washington was planted in the spring of 1990 with26,000 plants of the subject clone.

Clone RN29 was subsequently finally selected as a rootstock clone thatcontinues to possess growth and rooting characteristics that aredistinctly different from its M9 parent.

It distinguished itself in these beds from its M9 parent in thefollowing ways:

1. The subject clone produces many more lateral limbs (feathers) thanits M9 parent and grows more robustly in the stoolbed (FIGS. 2 and 3,Charts 1 and 2). Average increases in height of the plants in thestoolbed for the RN29 is almost 30% more than for the M9 (FIG. 6, M9;FIG. 7, RN29) and the average increase in the numbers of feathersproduced is more than three-fold. There also occurs a great differencein the average length of the individual feathers produced (Chart 2).Because of the more robust growth and increased number of limbs producedby the RN29, a two-fold difference also occurs in the number of leavesproduced per stoolbed plant (Chart 2). The number of nodes/shoot and theaver- age individual stem circumference were also greater for RN29 dueto its more robust growth habit. Leaf size (adding the length and widthtogether) and the length of the petioles were consistently smaller thanthe virus-free M9 (Chart 3).

                  CHART 1                                                         ______________________________________                                        Percent of Layer Plants with Side Limbs (Feathers)                            (Test Stooling Beds at Bordeaux, France)                                              Year                                                                  Rootstock Clone                                                                         79/80    80/81  81/82  82/83                                                                              Average                                 ______________________________________                                        M9 (virus-free)                                                                         13       8      25     0    11.5                                    RN8       8        6      13     0    6.8                                     RN19      41       32     44     19   34.0                                    RN29      39       22     35     15   27.8                                    ______________________________________                                    

                  CHART 2                                                         ______________________________________                                        Growth Characteristics                                                        (Test Stooling Beds at Ephrata, Washington)                                        Length  Number  Number Length                                                                              Number                                      Root-                                                                              of      of      of     of    of    Circumference                         stock                                                                              Shoot   Nodes/  Spura/ Spur  Leaves/                                                                             of Stem                               Clone                                                                              (cm)    Shoot   Shoot  (cm)  Shoots                                                                              (cm)                                  ______________________________________                                        H9   66.80*  39.20   3.00   1.50  53.00 3.24                                  RN8  62.10   42.10   1.80   1.20  57.20 3.80                                  RN19 78.20   41.00   18.60  8.60  88.30 3.51                                  RN29 86.20   45.60   21.40  10.30 100.00                                                                              3.54                                  ______________________________________                                         *All numbers shown are the average of 100 plants selected at random.     

                  CHART 3                                                         ______________________________________                                        Leaf Size and Respective Petiole                                              Length of Respective Rootstock                                                (Test Stooling Beds at Bordeaux, France)                                      Rootstock                                                                              Length, L                                                                              Width, W   L + W Length of                                  Clone    (mm)     (mm)       (mm)  Petiole                                    ______________________________________                                        M9       101.7    63.8       165.5 32.5                                       (virus free)                                                                  RN8      98.8     73.6       172.4 34.0                                       RN19     91.4     60.0       151.4 30.8                                       RN29     85.5     57.1       142.6 28.5                                       ______________________________________                                    

2. The subject clone has the ability to produce many more rooteddaughter plants per mother plant (FIG. 1) and per meter of stoolbed rowthan its M9 parent (Charts 4, 5 and 6). Data collected at the Deveaux,Belgium test site shows a two-fold increase in rooting ability and inthe number of rooted plants harvested (Charts 1 and 2) and at a testsite at Bordeaux, France a three-and-one-half-fold increase isdemonstrated after five years in the stoolbed (Chart 6).

                  CHART 4                                                         ______________________________________                                        RN29 Stoolbed Production (Deveaux, Belgium)                                   ______________________________________                                        No. Mother Plants - 1,875                                                     Length of Bed (m) - 6,215                                                     Year                                                                          Grade (mm)                                                                            82/83   83/84    84/85  85/86  86/87                                  ______________________________________                                        10/12   1,700   900      1,450  3,050  2,500                                   8/10   0       0        2,100  0      0                                       6/10   20,600  16,400   0      0      13,850                                 6/8     0       0        13,040 13,500 0                                      5/7     0       0        0      0      0                                      4/6     11,400  11,200   17,200 11,400 20,100                                 04      0       3,100    0      4,900  1,050                                  #2s     4,500   3,900    4,000  4,400  7,900                                  Totals  38,200  35,500   37,790 37,250 45,400                                 Per Mother                                                                            20.37   18.93    20.15  19.87  24.21                                  Plant                                                                         Per Meter                                                                             61.12   56.80    60.46  59.60  72.64                                  ______________________________________                                        Year                                                                          Grade (mm)                                                                            87/88   88/89    89/90  90/91                                         ______________________________________                                        10/12   2,100   0        1,200  1,650                                          8/10   5,150   7,050    6,050  0                                              6/10   0       0        0      20,900                                        6/8     14,200  15,200   13,800 0                                             5/7     0       0        0      0                                             4/6     1,400   14,500   15,900 14,100                                        04      0       0        0      0                                             #2s     7,500   4,300    10,800 4,700                                                                                Average                                Totals  30,350  41,050   47,750 41,350 82/91                                  Per Mother                                                                            16.19   21.89    25.47  22.05  21.02                                  Plant                                                                         Per Meter                                                                             48.56   65.68    76.40  66.16  63.05                                  ______________________________________                                    

                  CHART 5                                                         ______________________________________                                        M9(Virus-Free) Stoolbed Production (Deveaux, Belgium)                         ______________________________________                                        No. Mother Plants - 561                                                       Length of Bed (m) - 187                                                       Year                                                                          Grade (mm)                                                                            82/83   83/84    84/85  85/86  86/87                                  ______________________________________                                        10/12   225     100      250    750    464                                     8/10   0       0        450    0      0                                       6/10   4,150   2,950    0      2,350  2,200                                  6/8     0       0        3,400  0      0                                      5/7     0       0        0      0      0                                      4/6     1,800   1,600    2,200  1,600  3,000                                  04      0       300      0      0      0                                      #2s     700     800      500    500    1,400                                  Totals  6,875   5,750    6,800  5,200  7,064                                  Per Mother                                                                            12.25   10.25    12.12  9.27   12.59                                  Plant                                                                         Per Meter                                                                             36.76   30.75    36.36  27.81  37.78                                  ______________________________________                                        Year                                                                          Grade (mm)                                                                            87/88   88/89    89/90  90/91                                         ______________________________________                                        10/12   75      --       --     --                                             8/10   450     --       --     --                                             6/10   0       --       --     --                                            6/8     2,700   --       --     --                                            5/7     0       --       --     --                                            4/6     2,200   --       --     --                                            04      0       --       --     --                                            #2s     400     --       --     --                                                                                   Average                                Totals  5,825   --       --     --     82/91                                  Per Mother                                                                            10.38   --       --     --     11.14                                  Plant                                                                         Per Meter                                                                             31.15   --       --     --     33.43                                  ______________________________________                                    

                  CHART 6                                                         ______________________________________                                        Average Number of Plants Per Stoolbed Mother Plant                            (Test Stooling Beds at Bordeaux, France)                                               Year Planted and Age                                                 Rootstock  79/80    80/81  81/82  82/83                                       Clone      2-Yr     3-Yr   4-Yr   5-Yr Average                                ______________________________________                                        M9 (virus-free)                                                                          1.2      2.6    .5     4.0  8.3                                    RN8        2.1      3.9    3.8    6.4  16.2                                   RN19       2.6      4.4    6.5    9.1  22.6                                   RN29       4.4      5.6    5.7    11.3 27.0                                   ______________________________________                                    

3. Small differences in leaf color and structure have also been noticed.Leaf color of the subject clone is a pale yellow-green as compared toM9's darker green color (FIG. 5) RN29 is also characterized with leaveswhich exhibit smaller and sharper serrations than does its M9 parent(FIG. 4).

4. The lack of blooming characteristics of RN29 is very pronounced andin this respect differs distinctly from its M9 parent. The lack of anybloom produced on RN29 two-year-old line-out stocks was contrasted withthe amount exhibited by the M9 parent (chart 7).

                  CHART 7                                                         ______________________________________                                        Bloom Characteristics                                                         (Research Station at Gorsum, Belgium - 1985)                                               % of Rootstocks With Bloom                                       Rootstock Clone                                                                            (1 Year From Stoolbed)                                           ______________________________________                                        RN8          29                                                               RN19         4                                                                RN29         0                                                                M9 (virus-free)                                                                            15                                                               ______________________________________                                    

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows typical root growth following one season in the stoolbed.

FIG. 2 shows numerous lateral branches and pale yellow-green color ofleaves on new shoots.

FIG. 3 shows numerous lateral branches (feathers).

FIG. 4 shows the fine leaf serrations.

FIG. 5 shows the pink top growth of new shoots with the paleyellow-green color of older leaves.

FIG. 6 shows the average height in centimeters of M9 rootstock daughterplants in a stoolbed row in Ephrata, Wash.

FIG. 7 shows the average height in centimeters of RN29 rootstockdaughter plants in a stoolbed row in Ephrata, Wash.

DESCRIPTION OF VEGETATIVE CHARACTERISTICS

The following is a detailed description of the new apple rootstocksgrowth characteristics based on the stoolbed plants grown at the sixtest sites described above. Colors of the leaves and shoots are based ontheir appearance at the sites where grown. In those instances where aprecise color assessment can be made, reference is to the Munsell LimitColor Cascade Table. In other instances, general color terms are used inaccordance with the ordinary dictionary significance.

General habit:

Strength of growth.--Vigorous, stiff.

Habit.--Upright.

Branching.--Many, flexible, willowy.

Vegetative Shoots:

Bark color.--Greenish-brown (22-14).

Pubescence.--Finely tomentose.

Lenticels.--Few, inconspicuous, widely spaced, small, yellow-white.

Leaves:

Size.--Average, 5.7 cm wide, 8.6 cm long.

Shape.--Broad elliptic, somewhat asymmetric, wavy.

Base.--Obtuse, attenuated.

Apex.--Mucronate.

Serrations.--Finely serrate at sides, more obtuse margins at base.

Spacing.--Normal phyllotaxical arrangement for Malus.

Color.--Pale yellow-green (22-11) with pinkish tips.

Leaf scars:

Shape.--Broad V, slightly raised.

Color.--Dark brown.

Petioles:

Shape.--Slender, slightly channeled.

Length.--Medium, 2.85 cm.

Color.--Reddish-brown (32-12).

Pose.--Slight acute angle near tip, mostly horizontal.

Glands.--None.

Stipules:

Size.--Small, 3-5 mm, inconspicuous, some minutely serrated.

Color.--Yellow-green.

Pose.--Mostly reposed along petiole.

Lateral buds:

Size.--Small.

Shape.--Flat, angular.

Color.--Dark brown.

Pubescence.--Fine hairs, tomentose.

Apical buds:

Size.--Larger than lateral buds.

Shape.--Obtuse.

Color.--Dark brown.

Pubescence.--Tomentose.

Dormant Plant

Shoots:

Size.--Stocky, 7.8-12.0 mm in caliper at base, stiff, brittle.

Bark color.--Dark brown (25-15).

Pubescence.--Conspicuously pubescent.

Nodes.--Larger in diameter than internodes with shoulder at each side onleaf scar.

Internodes.--Smooth, regularly spaced.

Stooling and Root Characteristics

Rooting and stooling: Multiplies well in stoolbeds, forming strong rootsalong full length of shank. Roots arise from nodes.

Flower Characteristics

Flowers:

Size.--3.5 cm in diameter.

Color.--White with pinkish streaks toward base.

Fruit (No commercial value but useful for identification):

Shape.--Round to slightly oblong. Color.--Red stripes. Size.--4.5 cm indiameter, 5.5 cm in length. Flavor.--Bland, tasteless.

General Characteristics

Rootsuckering: Slight.

Size control potential: Size of trees budded on the subject rootstockswill vary according to the vigor of the cultivar, condition and type ofsoil and orchard management. "Standard" growing cultivars such as Redand Golden Delicious are reduced in size about 65% when compared totrees on apple seedling rootstocks. Less vigorous varieties are morereduced in size and more vigorous varieties are less reduced in size.

Dwarfing: Fully dwarfing.

Precocity: Varies according to variety, most cultivars often flower andset fruit the first year in the orchard and thereafter bear fruit eachyear.

Compatibility: Graft compatible with all major commercial fruitingvarieties.

Root anchorage: Needs support.

Hardiness: Hardy in most commercial apple growing areas.

Disease and pest resistance: Average resistance to common diseases andpests of apple. Tested and found free of all known virus and virus-likediseases to apple.

What is claimed is:
 1. A new and distinct apple tree clone, a sport of the Malling 9, referred to by the cultivar designation `M9-RN29`, substantially as herein shown and described, characterized particularly by its ability to serve as a root-stock for grafting of apple tree cultivars to produce dwarf apple trees and by its ability to root very readily in the stoolbed and produce high quality stoolbed rootstock plants for nursery use. 